degeneration vs pejoration

degeneration

noun
  • The process or state of growing worse, or the state of having become worse. 

  • That condition of a tissue or an organ in which its vitality has become either diminished or perverted; a substitution of a lower for a higher form of structure. 

  • Gradual deterioration, from natural causes, of any class of animals or plants or any particular organ or organs; hereditary degradation of type. 

  • A thing that has degenerated. 

pejoration

noun
  • The act or process of becoming worse; worsening or degeneration. 

  • The process by which a word acquires a more negative meaning over time. 

How often have the words degeneration and pejoration occurred in a corpus of books? (source: Google Ngram Viewer )